“[T]he immune system is a metaphor for the self. Its ostensible job is the defense of the organism, but it is potentially a treacherous defender, like the Praetorian guard that turns its swords against the emperor. Just as the immune system can unleash the inflammations that ultimately kill us, the self can pick at a psychic scar - often some sense of defeat or abandonment - until a detectable illness appears, such as obsessive-compulsive disorder, depression, or crippling anxiety.”